Harnessing Variable Renewables: Where is the Beef?

The International Energy Agency (IEA) has just published a book titled "Harnessing Variable Renewables: a Guide to the Balancing Challenge." Variable renewables refers to solar and wind power generated electricity. Balancing refers to making the grid stable when solar and wind generated electricity are plugged in.

In the best of all possible worlds such a book would be available for free down load on the Internet, so that retired guys like me, who study reports about energy technology, but who cannot afford expensive books, can look at them. Unfortunately downloading this book from the IEA will cost me €80, and 80 Euros is a little steep for me, especially as I am probably going going to find the download useless once I finish writing my review.

Why so expensive? The Press Release answers that question nicely,

Written for decision makers . . .

That means that tax payers, and rate payers will be expected to pay the bill. Hay even the IEA is not above grubbing for money when it finds deep pockets.

"Harnessing Variable Renewables" appears to be a will it work study, intended for decision makers. A will it work study is one which examines a concept and determines whether it is viable in the real world. The IEA press release explains,

Power systems must be actively managed to maintain a steady balance between supply and demand. This is already a complex task as demand varies continually. But what happens when supply becomes more variable and less certain, as with some renewable sources of electricity like wind and solar PV that fluctuate with the weather? To what extent can the resources that help power systems cope with the challenge of variability in demand also be applied to variability of supply? How large are these resources? And what share of electricity supply from variable renewables can they make possible?

There is no one-size-fits-all answer. The ways electricity is produced, transported and consumed around the world exhibit great diversity. Grids can cross borders, requiring co-ordinated international policy, or can be distinct within a single country or region. And whether found in dispatchable power plants, storage facilities, interconnections for trade or on the demand side, the flexible resource that ensures the provision of reliable power in the face of uncertainty likewise differs enormously.

Thus the question decision makers who are addressed in "Harnessing Variable Renewables" will be asking is can the variable electrical output from renewables be balanced on the grid, how can it be balanced. First the conclusion of "Harnessing Variable Renewables" that some variable renewables can be balanced is not new. Even many renewable critics acknowledge that. The real question is not will it work, but how much will it cost to make it work. Costs are the beef in the part of the title that asks, "Where is the Beef." The IEA press release is silent about costs, and so we are left to wonder if the IEA book addresses cost issues. So far none of the reviews of "HVR" I have run across mention costs, yet I would hope that decision makers would would want to know how much a balanced variable renewable grid system would cost, before the give the go ahead to implement such a system.

Reviews of "HVR" are suggestive. For example offshoreWIND.biz tells us,

Assessing flexible resources

Harnessing Variable Renewables: a Guide to the Balancing Challenge lays out a four-step method for assessing existing flexible resources, which can then be used to balance increasingly variable supply and demand. Step one of this Flexibility Assessment (FAST) method assesses the ability of the different flexible resources to change their production or consumption; step two examines the aspects of the power system that will constrain them from doing so; step three calculates the maximum requirement for flexibility of a given system resulting from fluctuating demand and output from wind plants and the like; and step four identifies how much more variability can be balanced with existing flexible resources.

The book features eight case studies in which the FAST Method is applied to eight geographic areas with very different characteristics. The resulting analysis shows that each region has the technical resources to balance large shares of variable renewable energy.

Potentials range from 19% in the least flexible area assessed (Japan) to 63% in the most flexible area (Denmark). The IEA also assessed the resources of the British Isles (Great Britain and Ireland together), 31%; the Iberian Peninsula (Spain and Portugal together), 27%; Mexico, 29%; the Nordic Power Market (Denmark, Finland, Norway and Sweden), 48%; the Western Interconnection of the United States, 45%; and the area operated by the New Brunswick System Operator in Eastern Canada, 37%.

This range of results is due to the different flexible resources found in these areas. Norway, for example, has extensive hydropower, which is a very flexible resource; while Japan’s power plants, many of which run on nuclear and coal, are not as flexible (e.g. it takes longer for these sources to respond to fluctuations in demand).

Thus the assumption by the the IEA researchers is that grid managers will draw on existing grid resources to back up renewable energy. The study finds in effect that their are limitations to renewable grid penetration posed by reliance on existing grid resources. Indeed in most countries renewable grid penetration of less than 50% will be possible are using existing grid resources for balancing.

This means that for most countries a high renewables grid penetration system discussed in "HVR" is only at best a bridge to the 4/5th fossil fuel reduction that climate scientists envision us requiring by 2050. But can a renewables only system take us all the way to an energy future than produces only 20% of the CO2 produced today by fossil fuels?

There are clearly grounds for doubt, and clearly grounds for wondering it is going to be possible to produce 80% of all energy resources through reliance on renewables, how much will it cost to do so.

As I have pointed out decision makers need to know how much a balanced high renewables penetration system will cost. If "HVR" addressed the cost issue and offered good news, the pro-renewable reviewers, and indeed the press release would have mentioned that fact. If it did not address cost issues, then decision makers lack important information that are required to make appropriate decisions or the future sources of post-carbon energy.

Since I have no information on costs related to the "HVR" case studies, I will have to go with my own case studies, and since the United States Western Interconnect is one of the cases studied, I will note a previous Nuclear Green post, "The cost of carbon mitigation with renewables." In that post I discussed the Eastern Wind Integration and Transmission Study and , How do Wind and Solar Power Affect Grid Operations: The Western Wind and Solar Integration Study.These studies looked at 30% to 35% renewablea penetration of the two largest North American interconnects. Not quite as high as the 48% maximum penetration which "HVR" envisioned for the Western Interconnection. I noted that there were both significant connections about the actual CO2 mitigation that

As with all National Renewables Energy Laboratory reports, the WWSIS made no attempt to compare renewables costs and performance with nuclear power. But a relatively simple thought experiment can yield some very telling results. First we can assume that nuclear power will displace coal rather than CCGT. The Energy Information Agency estimates that the levelized cost of Advanced Nuclear will be 119.0, or about 12 cents per kWh. If nuclear displaces coal at that cost, the cost of displacing one ton of CO2 would be $119. Now let us take the 11% renewables case. The 2016 levelized cost of wind is 149.3, while the levelized cost of solar thermal is 256.6. Thus the average levelized cost of the 11% renewables is 159.08, and the cost of displacing a ton of CO2 with renewables is $159.0 + transmission costs and other hidden cost of wind generation systems, and the added CO2 emissions of fossil fuel wind backups kept spinning. plus the added CO2 efficiencies of fossil fuel generators used in load leveling and load following roles. Since wind is displacing relatively carbon efficient CCGTs rather than carbon inefficient coal fired generating plants. each MW of CCGT power displaced would produce 800 pounds of CO2, rather than a ton of CO2 produced by the equivalent electrical output of a coal fired power plant. Thus carbon mitigation with the 11% wind April scenario will cost about $400 + hidden costs or over three times as much as nuclear power would costs.

In the April 35% penetration case, wind becomes the predominate source of electricity on most days, and it displaces 2/3rds of coal generation capacity and all the CCGTs. Yet for the July 35% penetration case, wind failed to displace most CCGTs and no coal. Thus the WWSIS study data reported provided in sufficient information for understanding the the potential carbon mitigation costs . However it should be noted that the DoE study, Eastern Wind Integration and Transmission Study(EWITS) found that the cost of total system electrical output increased dramatically as wind penetration rose to 30%.

I concluded that,

Clearly then increasing wind penetration in the West will increase the level of carbon mitigation as well as its costs. It is also clear that wind displaces CCGTs before it displaces coal, and this increases the cost of carbon mitigation by wind significantly. Carbon mitigation with conventional nuclear would thus appear well over 3 times more cost effective compared to carbon mitigation with wind. The true cost effectiveness advantage of nuclear cannot be gaged until we know more about the hidden costs of wind, but the hidden costs appear to extract greater cost penalties at higher levels of wind grid penetration.

These conclusions suggest that Wind and Solar energy at high penetrations may not be cost effective tools for carbon mitigation. Taken all together, what we know about the contents of "HVR" is consistent with variable renewables being a questionable and expensive bridge to a low carbon future.